A facile synthetic route to poly(p-phenylene terephthalamide) with dual functional groups.

Claisen rearrangement reaction was employed for the first time to obtain a novel PPTA bearing reactive allyl and hydroxyl groups which may act as a sizing agent of Kevlar fibers to improve the interface structure and interfacial adhesion of rubber or epoxy based composites.

On the effectiveness of shelter-in-place as a measure to reduce harm from atmospheric releases.

Shelter-in-place (SIP) is recommended by numerous entities as a measure to reduce harm in the event of a chemical accident or chemical attack taking place in the atmosphere. This article, based on solving mass conservation equation for indoor hazardous material, examines how effective SIP is to reduce the harm. It is shown that SIP can be effective when the shelter's air exchange rate is low and when the release duration is short. The effectiveness is strongly affected by the hazardous material itself: SIP is more effective for hazardous material with higher toxic load exponent. Another finding is that leaving the shelter promptly after the event can also be critical.

[Method for determining 2, 4-D butylate in serum by gas chromatography].

OBJECTIVE: To establish a method for determining 2, 4-D butylate in serum by gas chromatography (GC)and to provide a basis for the diagnosis and treatment of clinical poisoning. METHODS: Serum 2, 4-D butylate level was determined by the following steps: mixing serum (0.5 ml)with trichloromethane (2.0 ml), adequately shaking for extraction, standing for 5 min, centrifuging at 4 000 rpm for 10 min, blow-drying the trichloromethane layer with nitrogen, adding ethanol (50 µl)to a certain volume, adding the sample (1.0 µl), and performing GC with a hydrogen flame ionization detector. RESULTS: Serum 2, 4-D butylate level showed a linear relationship within 5∼40 µg/ml, with a regression equation of y = 1 831.6.4x-899.4 (r = 0.999 2); the minimum detectable concentration was 1.0 µg/ml. The recovery rate was 88.7%∼103.0% (relative standard deviation (RSD) 3.8%∼5.0%). The intra-day RSD and inter-day RSD were 3.87-4.92% and 3.33%∼5.34%, respectively. CONCLUSION: This determination method is simple, efficient, and accurate and provides a good means for rapid diagnosis and treatment of 2, 4-D butylate poisoning.

Tunable, luminescent, and self-healing hybrid hydrogels of polyoxometalates and triblock copolymers based on electrostatic assembly.

Hybrid hydrogels based on electrostatic co-assembly of polyoxometalates and ABA triblock copolymers were readily prepared and exhibit excellent luminescence and self-healing performance.

[Method for determining concentration of dichlorvos in serum by gas chromatography].

OBJECTIVE: To develop a method for determining the concentration of dichlorvos in serum by gas chromatography and to provide a basis for clinical diagnosis and monitoring of dichlorvos poisoning. METHODS: The serum (0.5 ml)collected from patients with dichlorvos poisoning was mixed with ethyl acetate (2.0 ml) and underwent shaking/extraction; the obtained liquid was subjected to standing (5 min) and centrifuging (4000 rpm); the obtained supernatant was collected and blow-dried with nitrogen and was then dissolved in ethanol (50 µl); 1.0 µl of the obtained liquid was collected and loaded into a glass-packed column; gas chromatography was performed using a nitrogen-phosphorus detector. RESULTS: A linear relationship was found when the concentration of dichlorvos in serum was 5.0 ∼ 50.0 µg/ml, with a regression equation of y = 804.13x-691.8 (r = 0.9992). The minimum detectable concentration was 2.0 µg/ml, the recovery rate was 86.8% ∼ 94.5%, the relative standard deviation (RSD) was 4.6% ∼ 5.5%, with an intra-day RSD of 4.52% ∼ 5.21% and an inter-day RSD of 3.56% ∼ 5.52%. CONCLUSION: This determination method is easy to operate, efficient, and accurate, and can be used for quickly diagnosing dichlorvos poisoning and quantitatively evaluating treatment outcome.

Do earthquakes exhibit self-organized criticality?

If earthquakes are phenomena of self-organized criticality (SOC), statistical characteristics of the earthquake time series should be invariant after the sequence of events in an earthquake catalog are randomly rearranged. In this Letter we argue that earthquakes are unlikely phenomena of SOC because our analysis of the Southern California Earthquake Catalog shows that the first-return-time probability PM(T) is apparently changed after the time series is rearranged. This suggests that the SOC theory should not be used to oppose the efforts of earthquake prediction.